diff --git a/src/clucy/core.clj b/src/clucy/core.clj
index a08db80..f7f5e1a 100644
--- a/src/clucy/core.clj
+++ b/src/clucy/core.clj
@@ -8,7 +8,8 @@
            (org.apache.lucene.queryparser.classic QueryParser)
            (org.apache.lucene.search BooleanClause BooleanClause$Occur
                                      BooleanQuery IndexSearcher Query ScoreDoc
-                                     Scorer TermQuery)
+                                     Scorer TermQuery
+                                     Explanation ComplexExplanation)
            (org.apache.lucene.search.highlight Highlighter QueryScorer
                                                SimpleHTMLFormatter)
            (org.apache.lucene.util Version AttributeSource)
@@ -60,18 +61,20 @@
      (add-field document key value {}))
 
   ([document key value meta-map]
-     (.add ^Document document
-           (Field. (as-str key) (as-str value)
-                   (if (false? (:stored meta-map))
-                     Field$Store/NO
-                     Field$Store/YES)
-                   (if (false? (:indexed meta-map))
-                     Field$Index/NO
-                     (case [(false? (:analyzed meta-map)) (false? (:norms meta-map))]
-                       [false false] Field$Index/ANALYZED
-                       [true false] Field$Index/NOT_ANALYZED
-                       [false true] Field$Index/ANALYZED_NO_NORMS
-                       [true true] Field$Index/NOT_ANALYZED_NO_NORMS))))))
+     (let [field (Field. (as-str key) (as-str value)
+                         (if (false? (:stored meta-map))
+                           Field$Store/NO
+                           Field$Store/YES)
+                         (if (false? (:indexed meta-map))
+                           Field$Index/NO
+                           (case [(false? (:analyzed meta-map)) (false? (:norms meta-map))]
+                             [false false] Field$Index/ANALYZED
+                             [true false] Field$Index/NOT_ANALYZED
+                             [false true] Field$Index/ANALYZED_NO_NORMS
+                             [true true] Field$Index/NOT_ANALYZED_NO_NORMS)))]
+       (if-let [boost (:boost meta-map)]
+         (.setBoost field boost))
+       (.add ^Document document field))))
 
 (defn- map-stored
   "Returns a hash-map containing all of the values in the map that
@@ -100,6 +103,17 @@
       (add-field document :_content (concat-values map)))
     document))
 
+(defn has-children? [exp]
+  (if-let [details (.getDetails exp)]
+    (> (alength details) 0)))
+
+(defn explain->map [^Explanation exp]
+  (conj {:description (.getDescription exp)
+          :value (.getValue exp)
+          :match? (.isMatch exp)}
+        (when (has-children? exp)
+          {:children (map explain->map (.getDetails exp))})))
+
 (defn add
   "Add hash-maps to the search index."
   [index & maps]
@@ -127,20 +141,24 @@
   ([^Document document score]
      (document->map document score (constantly nil)))
   ([^Document document score highlighter]
+     (document->map document score (constantly nil) nil))
+  ([^Document document score highlighter explanation]
      (let [m (into {} (for [^Field f (.getFields document)]
                         [(keyword (.name f)) (.stringValue f)]))
            fragments (highlighter m) ; so that we can highlight :_content
            m (dissoc m :_content)]
        (with-meta
          m
-         (-> (into {}
-                   (for [^Field f (.getFields document)
-                         :let [field-type (.fieldType f)]]
-                     [(keyword (.name f)) {:indexed (.indexed field-type)
-                                           :stored (.stored field-type)
-                                           :tokenized (.tokenized field-type)}]))
-             (assoc :_fragments fragments :_score score)
-             (dissoc :_content))))))
+         (conj
+          (-> (into {}
+                    (for [^Field f (.getFields document)
+                          :let [field-type (.fieldType f)]]
+                      [(keyword (.name f)) {:indexed (.indexed field-type)
+                                            :stored (.stored field-type)
+                                            :tokenized (.tokenized field-type)}]))
+              (assoc :_fragments fragments :_score score)
+              (dissoc :_content))
+          (when explanation {:explain (explain->map explanation)}))))))
 
 (defn- make-highlighter
   "Create a highlighter function which will take a map and return highlighted
@@ -172,7 +190,7 @@ fragments."
 (defn search
   "Search the supplied index with a query string."
   [index query max-results
-   & {:keys [highlight default-field default-operator page results-per-page]
+   & {:keys [highlight default-field default-operator page results-per-page explain]
       :or {page 0 results-per-page max-results}}]
   (if (every? false? [default-field *content*])
     (throw (Exception. "No default search field specified"))
@@ -191,13 +209,16 @@ fragments."
             start (* page results-per-page)
             end (min (+ start results-per-page) (.totalHits hits))]
         (doall
-         (with-meta (for [hit (map (partial aget (.scoreDocs hits))
-                                   (range start end))]
+         (with-meta (for [[pos hit] (->> (map (partial aget (.scoreDocs hits))
+                                              (range start end))
+                                         (map-indexed vector))]
                       (document->map (.doc ^IndexSearcher searcher
                                            (.doc ^ScoreDoc hit))
                                      (.score ^ScoreDoc hit)
 
-                                     highlighter))
+                                     highlighter
+                                     (when explain
+                                       (.explain searcher query pos))))
            {:_total-hits (.totalHits hits)
             :_max-score (.getMaxScore hits)}))))))
 
diff --git a/test/clucy/test/core.clj b/test/clucy/test/core.clj
index 07bc0a4..2fbbe62 100644
--- a/test/clucy/test/core.clj
+++ b/test/clucy/test/core.clj
@@ -69,4 +69,26 @@
       (is (== 1 (count (search index "m*" 10 :page 1 :results-per-page 3))))
       (is (empty? (intersection
                     (set (search index "m*" 10 :page 0 :results-per-page 3))
-                    (set (search index "m*" 10 :page 1 :results-per-page 3))))))))
+                    (set (search index "m*" 10 :page 1 :results-per-page 3)))))))
+
+  (testing "Explanations"
+    (let [i (memory-index)]
+      (apply add i people)
+      (let [exp (-> (search i "Miles" 10 :explain true)
+                    (first)
+                    (meta)
+                    (:explain))]
+        (is (map? exp))
+        (is (:match? exp))
+        (is (string? (:description exp)))
+        (is (float? (:value exp)))
+        (is (seq? (:children exp))))))
+
+  (testing "Boosting"
+    (let [i (memory-index)]
+      (add i
+           (with-meta {:planet "Earth Mk. II" :designer "Slartibartfast"}
+             {:name {:boost 0.0}})
+           (with-meta {:planet "Earth" :designer "Slartibartfast"}
+             {:name {:boost 1.0}}))
+      (is (= "Earth" (:planet (first (search i "Slartibartfast" 2))))))))